linux-kernel - Re: [PATCH 1/3] cpumask: add for_each_online_cpu_mask

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Date:	Fri, 12 Sep 2008 07:17:08 -0700
From:	Mike Travis <travis@....com>
To:	Rusty Russell <rusty@...tcorp.com.au>
CC:	Ingo Molnar <mingo@...e.hu>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	"H. Peter Anvin" <hpa@...or.com>, Jack Steiner <steiner@....com>,
	Jes Sorensen <jes@....com>, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/3] cpumask: add for_each_online_cpu_mask_nr function

Rusty Russell wrote:
> On Wednesday 10 September 2008 01:50:14 Mike Travis wrote:
>>   * Add for_each_online_cpu_mask_nr() function to eliminate need for
>>     a common use of a temporary cpumask_t variable.  When the following
>>     procedure is being used:
>>
>>     funcproto(cpumask_t *mask, ...)
>>     {
>> 	cpumask_t temp;
>>
>> 	cpus_and(temp, *mask, cpu_online_map);
>> 	for_each_cpu_mask_nr(cpu, temp)
>> 		...
>>
>>     If then becomes:
>>
>>     funcproto(cpumask_t *mask, ...)
>>     {
>> 	for_each_online_cpu_mask_nr(cpu, *mask)
>> 		...
>>
>>   * Note the generic __next_cpu_and (and __next_cpu_and_nr) functions
>>     allowing AND'ing with any cpumask_t variable, not just the
>> cpu_online_map.
> 
> Good idea!  But I really dislike the _nr versions (too many names!).  Do we 
> really need them, since by definition cpus after nr_cpu_ids are never 
> online...
> 
> (And we should initialize nr_cpu_ids to NR_CPUS so even early boot works, if 
> we don't already...).
> 
> Cheers,
> Rusty.

Yes, the only reason the _nr is there is to be consistent with the
current for_each_cpu_mask{,_nr} functions.  What I'd like to do is
convert all calls to use the nr_cpu_ids and if there's some reason
to need to iterate over NR_CPUS range, then you'd use FOR_EACH_CPU_MASK.

And yes, nr_cpu_ids is init'd to NR_CPUS.

Thanks,
Mike
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